The invention relates to system for interrupting spark ignition of a marine propulsion internal combustion engine to reduce engine speed and facilitate shifting of a marine propulsion transmission.
Various systems are known in the prior art for interrupting spark ignition to reduce engine speed during shifting to ensure positive engagement for reversing propeller rotation. Resistance to shifting is typically sensed because this indicates improper transmission engagement. It is known to provide a single ignition interruption for a specified length of time, or to interrupt ignition periodically through a definite timing sequence, or to provide a variable sequence according to engine operating characteristic variables. The periodic interruption may be provided by a first timer, and the overall length of the sequence may be determined by a second timer establishing an overall cycle. It is also known to sense engine rpm and establish ignition-off as long as the rpm is above a set point, and ignition-on as long as the rpm is below this set point. This prevents the engine from dying by restoring ignition when the rpm falls below the set point.
In the present invention, a stall interval is provided and the engine is intentionally stalled upon completion of such interval if the shifting is not completed, even if engine speed has dropped below a given cut-in speed.